• Cattle avoidance of leafy spurge: A case of conditioned aversion

      Kronberg, S. L.; Muntifering, R. B.; Ayers, E. L.; Marlow, C. B. (Society for Range Management, 1993-07-01)
      Leafy spurge (Euphorbia esula L.) represents a serious threat to the productivity and profitability of many cattle ranches in the midwestern U.S. Sheep and goats will graze the weed, but cattle generally do not. We hypothesized that cattle avoid leafy spurge because it contains 1 or more chemicals that elicit a conditioned flavor aversion when consumed. First, we tested cattle to determine if they reduced their intake of a novel feed on subsequent days if we modestly increased rumen fill by introducing additional feed or additional feed plus an aversive agent (lithium chloride, LiCl) after they had consumed the novel feed. We observed that cattle became averted (P = .0001) to the novel feed only when LiCl was administered with additional feed. Simply increasing rumen fill by a small amount did not cause cattle to reduce their intake of the novel feed the following day. Secondly, we tested cattle to determine if they reduced their intake of a novel feed on subsequent days if we introduced leafy spurge into their rumina following consumption of the novel feed. We also tested cattle to determine if a spurge-induced aversion to a novel feed was preventable by inoculation with rumen microbes from sheep with spurge in their diets. We found that introducing spurge into cattle after their intake of novel feed reduced (P < .01) their intake of the novel feed on subsequent days. Cattle inoculated with rumen microbes from spurge-adapted sheep had similar (P > .40) aversions to a novel feed paired with spurge introductions. Apparently, cattle avoid leafy spurge partly or wholly because they develop a conditioned aversion after first ingesting some threshold amount of it.
    • Influence of Breed on Forage Intake of Range Beef Cows

      Kronberg, S. L.; Havstad, K. M.; Ayers, E. L.; Doornbos, D. E. (Society for Range Management, 1986-09-01)
      We estimated forage intake of Hereford (HH) and 75% Simmental-25% Hereford (3S1H) cows grazing in northcentral Montana during the summer grazing season of 1982. Cows ranged freely over a 81-ha pasture of rough fescue (Festuca scabrella)-dominated rangeland. Intake was estimated for 6 lactating (March calved) and 6 nonlactating cows of each breed type in June, July, August, and September, 1982. Fecal output of dry cows was measured with total fecal collections and was also estimated with the chromic oxide dilution technique. Only the chromic oxide technique was used for lactating cows. Three to 4 esophageal-fistulated cows of each breed type were used for collection of dietary material suitable for in vitro digestibility analysis. Organic matter intake (as a percentage of body weight per day, %BW/D) of nonlactating HH and 3S1H cows did not differ (P is greater than or equal to 10), averaging 1.3% BW/d (using total fecal collection estimates). Chromic oxide derived forage intake estimates were 15% higher (P<.10) than total fecal collection estimates. Breeds responded similarly (P4 1/4.10) to both fecal output estimation techniques. Forage intake estimates for lactating cows were adjusted for this overestimation, and lactating 3S1H cows consumed more (P<.10) forage than lactating HH cows (1.9 vs. 1.7% BW/d, and 10.9 vs. 7.8 kg/d, respectively).